Topic: Building a New Engine - Advice Needed

[stikman]

Hey guys, I've had this build in the works for a while now and my plan is to get it done for spring.  It'll be my main all-round ride, city jammer and highway cruiser.  It's another chopper, old hardtail frame with a +12 springer.  I'm looking for a bit of advice on a few choices for engine performance pieces.  I've currently got a NOS set of Wiseco 836 pistons I got from Bill P, my jugs are already bored.  I'll be porting the head myself.  Got multiple sets of roundtop carbs to choose from so will probably stick with those (w/ breadbox or v-stacks) and spend the rest of my "budget" elsewhere.

So one intake valve guide is chipped from a PO having bent a valve in the past.  I've been going back and forth on what to do about it, though I've decided there's no good reason to leave it be if I'm putting time and money into this head.  All the valves will be replaced anyway (PO didn't maintain valve lash and they got pretty hammered), so what are your thoughts on going with bigger intake valves or just replacing the one guide and using fresh stock valves?  As it's a chopper I'm looking for more low/mid range than top end.  So I'm a bit unsure just how far to take my porting and intake valves, as I don't want to lose my low end torque gains.

Also trying to decide on a cam.  I've got a new Webcam 41 on the shelf, but since I decided on the Wisecos over the cast cruzinimage 836 kit I'd like to take advantage of the higher CR and valve reliefs.  Leaning toward the DP295 based on everything I've heard about it over the years.  The power range seems right for my application.


So to sum up:  What advice do you fellahs have on specific porting characteristics, intake valve size, and camshaft choice for my application of a hardtail chopper looking for mainly (but not exclusively) low and mid range torquey power on a 10.25:1 836 engine?  Thanks in advance!


Current Specs:

Dyna Ignition and Coils
Roundtop Carbs with Velocity Stacks or Breadbox
MAC Drag Pipes 4-4  (I know.. I know  )
Wiseco 836 Pistons
HD Head Studs
Titanium Valve Retainers
Porting specifics?
Intake valve size?
Camshaft?

[Sam Green Racing]

The DP295 cam is ideal for what you want, stacks of low to mid range power.

[Jerry Rxman Griffin aka MuthaF'er]

Can't go wrong with bigger valves. Bigger valves = more air = more gas = bigger bangs

[HondaMan]

With the Dyna ignition (I'm presuming a Dyna S?) and Dyna coils (if 3-ohm type), you will NOT be able to run around under 5k RPM. It will kill the battery. At the very least, you will need 5-ohm coils, or perhaps one of my Resistor Packs if you have the 3 ohm coils.

If you're going to the 4.00-16 rear wheel look, consider the 19T countersprocket from Cycle X. You must trim (grind) about 1/8" (3mm) from the tips of the teeth to prevent it tearing off the rubber chain cushion inside the sprocket's side cover, though. I ran this on my 750 for 2 years and liked it, but am going to larger tires now, so don't plan on using it until I hit the road for a longer ride.

For improved low-end torque...retard the intake valve opening timing, whatever cam you use. The max low-end torque in this engine can be found at no more than 5 degrees BTC opening for the intake valve, if the exhaust valve timing matches that number: if the exhaust opens sooner than the intake, it will be for higher RPM. If the exhaust opens later than the intake, it will spread the power out and lower the torque RPM curve in RPM. For example, the 750A cam opens 5-8 degrees AFTER TDC (at the least, many are more than this) to improve the low-end torque for the Auto. It works well, but limits the top RPM for asthmatic reasons: the "A" doesn't even come with a tach because it can't overrev itself in 1st gear, rather like Honda's S90 engine.

[MRieck]

 Larger valves only work if the seats are opened up to accommodate them. If you want torque use the 41 cam. The exhaust valve always opens before the intake valve closes with any aftermarket cam. With fixed lobe separation you cannot get creative.

[stikman]

Larger valves only work if the seats are opened up to accommodate them.

I'm sure the machine shop can open them up, and I should be able to smooth them in.  I can't seem to remember if I've read anything saying whether the 33.5mm intakes and complimentary porting will add more everywhere, high to low, or if they just kill low end power while allowing better breathing up high.  Most guys seem to be looking for all they can get in the higher revs on these engines, which doesn't exactly suit my program.  So you really figure the 41 will out perform the DP295 in the low/mid eh?

[PeWe]

1000cc give nicer low end It start a domino effect of other mods...

BUT, my bike worked really good with 836 stock carbs, ported head with 34mm inlet, cam Action Fours SS-1, stock rods, lightened alternator rotor.  17-48 gearing.
A good touring machine.
Maybe not perfect for a chopper since the engine started to scream and pull hard from 4500-6000 to 9500 rpm. It could cruise at around 100mph all day long as it had to on my holidays going to the sun and blue warm sea 2000 km away south.

[stikman]

With the Dyna ignition (I'm presuming a Dyna S?) and Dyna coils (if 3-ohm type), you will NOT be able to run around under 5k RPM. It will kill the battery. At the very least, you will need 5-ohm coils, or perhaps one of my Resistor Packs if you have the 3 ohm coils.

Running Dyna S and 5 Ohm coils.  Will be starting out with 18/48, go from there.

1000cc give nicer low end It start a domino effect of other mods...

BUT, my bike worked really good with 836 stock carbs, ported head with 34mm inlet, cam Action Fours SS-1, stock rods, lightened alternator rotor.  17-48 gearing.
A good touring machine.
Maybe not perfect for a chopper since the engine started to scream and pull hard from 4500-6000 to 9500 rpm. It could cruise at around 100mph all day long as it had to on my holidays going to the sun and blue warm sea 2000 km away south.

Yeah, no doubt  .  Thanks for that info, Per.

[Jerry Rxman Griffin aka MuthaF'er]

17/48!! You are talking about performance, right?! Best/easiest/cheapest place to start.

[754]

17 / 54   will do it..
 STIKMAN, I MAY HAVE A 410 head to sell, with the big valves before Christmas?

[MRieck]

17 / 54   will do it..
 STIKMAN, I MAY HAVE A 410 head to sell, with the big valves before Christmas?

I have a complete head kit for a 410....valves, springs, retainers, special keepers and bases. Will sell for a good price.